1. Field of the Invention
The present invention pertains to the field of x-ray imaging systems, including among other things, x-ray sources for diagnostic x-ray imaging systems.
2. Background
Real-time x-ray imaging is increasingly being utilized by medical procedures as therapeutic technologies advance. For example, many electro-physiologic cardiac procedures, peripheral vascular procedures, PTCA procedures (percutaneous transluminal catheter angioplasty), urological procedures, and orthopedic procedures benefit from the use of real-time x-ray imaging.
A number of real-time x-ray imaging systems are known. These include fluoroscope-based systems where x-rays are projected into an object to be x-rayed and shadows caused by relatively x-ray opaque matter within the object are detected on the fluoroscope located on the opposite side of the object from the x-ray source.
Reverse-geometry x-ray imaging systems are also known. In such systems, an x-ray tube is employed to generate x-ray radiation. Within the x-ray tube, high-energy charged particles are generated and focused on a small spot on the relatively large target of the tube, inducing x-ray radiation emission from that spot. The charged particles are deflected (electromagnetically or electrostatically) in a raster scan pattern or otherwise over the target. A small x-ray detector is placed at a distance from the target of the x-ray tube. The detector typically converts x-rays that strike it into an electrical signal in proportion to the detected x-ray intensity.
Known embodiments of x-ray imaging systems place the x-ray source above the patient, wherein each of the component parts of the x-ray scanning tube assembly are stacked on top of the other components, one component after another (e.g., from bottom to top, a vacuum envelop assembly below a charged particle generator, the charged particle generator below a high-voltage terminal assembly, etc.) In these systems, a high-voltage power supply receptacle is connected to the high-voltage terminal assembly with the longitudinal axis of the high voltage receptacle parallel with the projection axis of the charged particle generator.
When the x-ray imaging system is activated and radiation is projected from the x-ray scanning tube, the radiation is generally in a downward direction and some of the radiation scatters off the patient and the x-ray table supporting the patient. Since the radiation is in a generally downward direction the scattered radiation is directed predominantly in an upward direction towards the most sensitive portions of the body of the attending staff, namely the head and neck. Furthermore, since patients usually lie face up on an x-ray table, when a woman is being imaged, her breast tissue which is typically more sensitive than most other tissue types, is subjected to the direct radiation from the x-ray source.
Thus, there is a need for an x-ray imaging system that will minimize the risks to the patient and the attendant staff, as well as allow the x-ray imaging system to be more useful.